Effect of calcium soaps of fatty acids and administration of somatotropin on milk production, preovulatory follicular development, and plasma and follicular fluid lipid composition in high yielding dairy cows

The effect of fat and bovine somatotropin (bST) on preovulatory follicular hormones and lipids was evaluated by feeding cows for 150 d from parturitio n a control diet, a control diet pins 0.55 kg/d of calcium soaps of fatty a cids, or a control diet with 500 mg of bST injected every 14 d. Fourteen da ys after a synchronized or natural estrus, cows were injected with a PGF(2 alpha) analogue; 48 h later, follicular fluid from all ovarian follicles >8 mm was aspirated. Cows fed fat or injected with bST produced more milk and milk solids than did control cows, and cows on the bST treatment lost more body condition after calving than did cows on the other treatments. Both t reatments changed the proportion of estradiol-active follicles (>400 ng of estradiol/ml of follicular fluid) and the correlation between follicular fl uid estradiol concentration and the total number large follicles per cow. I n follicles aspirated between 60 and 90 DIM the percentage of estradiol-act ive follicles was 67, 40, and 0 for cows on the control, calcium soaps of f atty acids, and bST treatments, respectively. After 90 DIM, no differences existed between treatments in the percentage of estradiol-active follicles. Estradiol concentration in follicular fluid was correlated with DIM at fol licle aspiration (r = 0.51). The proportion of oleic acid in free fatty aci ds in plasma at 50 DIM was lower in control cows and was lower in follicula r fluid of estradiol-active follicles. Both calcium soaps of fatty acids an d bST had a considerable effect on follicular development and activity and the composition of fatty acids in follicles.